UV-Curable Polymer Nanocomposites Based on Poly(dimethylsiloxane) and Zirconia Nanoparticles: Reactive versus Passive Nanofillers

Abstract

As the need for high-refractive-index materials escalates to meet the growing demands for antireflective coatings and various photonic devices with robust mechanical properties, elastomeric polymer nanocomposites containing a high loading level of zirconia nanoparticles afford tremendous promise. In this study, the interactions between two functionalized zirconia nanoparticles, one reactive and the other passive, with a short-chain, UV-curable poly­(dimethylsiloxane) in solvent are systematically examined by dynamic rheology. The effects of surface functionality, as well as UV light intensity and nanoparticle loading, on the cross-linking behavior are elucidated, and both filled systems are observed to form cross-linked networks at loading levels of up to 85 wt % zirconia. The time required to achieve dynamic modulus crossover (indicating network formation) exhibits a power-law dependence on the UV light intensity for both systems at all zirconia contents. At high loading levels of the passive nanofiller (75 wt % zirconia), the resulting films appear opaque, possessing significantly higher turbidity than those containing reactive nanoparticles, which conversely yield films with low turbidity and high optical clarity at loading levels as high as 80 wt % zirconia. Reactive zirconia is more strongly incorporated into the polymer network than passive zirconia, as evidenced by values of the ultimate gel moduli, zirconia leaching from solvent-swelled films, and the topologies of cross-fractured surfaces.

Concentration-Dependent Layer Exfoliation of Black Phosphorus by Human Serum Albumin and Its Corresponding Biocompatibility Change

“…See the Supporting Information for the test conditions. Turbidity of LBP was analyzed at 600 nm light absorbance by a UV–vis spectrophotometer (Shimadzu UV-2700) …”

“…Turbidity of LBP was analyzed at 600 nm light absorbance by a UV−vis spectrophotometer (Shimadzu UV-2700). 25 Statistical Analysis. Reported data were obtained by calculating the mean ± standard deviation of triplicate experimental data.…”

Gelation Dynamics during Photo-Cross-Linking of Polymer Nanocomposite Hydrogels

“…Nanomaterial–polymer interactions often obscure the rheological signatures of chemical cross-links in the polymeric network, − indicating that synergistic nanomaterial–polymer interactions during gelation must be considered for dynamic applications of these materials. The final material properties and microstructure after gelation are also influenced by the overall formulation. − Generally, increasing the polymer concentration subsequently increases the network stiffness. , In contrast, the impact of nanomaterial concentration is challenging to predict due aggregation or flocculation of nanomaterials, , “network dilution” due to defects in the polymer network, − or heterogeneous local chemical environments near nanomaterial surfaces …”

“…Advances in photo-cross-linking have broadened the use of polymer hydrogels as tissue engineering scaffolds, − antifouling surfaces, − and photonic materials. − Polymer hydrogels are versatile materials comprising cross-linked polymer networks that are swollen in water. Polymer network formation by photo-cross-linking offers several advantages over conventional approaches such as thermal or redox-initiated cross-linking: it proceeds under mild reaction conditions including ambient temperature and moderate pH, and it enables spatiotemporal control upon tuning light intensity, exposure time, and illumination area. , This control is often leveraged to build complex hydrogel structures through additive manufacturing, , tunable photodegradation, − or surface patterning. − …”

“…63−65 Generally, increasing the polymer concentration subsequently increases the network stiffness. 38,62 In contrast, the impact of nanomaterial concentration is challenging to predict due aggregation or flocculation of nanomaterials, 9,59 "network dilution" due to defects in the polymer network, 66−68 or heterogeneous local chemical environments near nanomaterial surfaces. 63 This work explores the evolution of mechanical properties and gelation dynamics during photo-cross-linking of polymer nanocomposite hydrogels comprising multiarm PEG-anthracene and silica-coated nanocapsules.…”